traceroute implementation using TCP packets
The more traditional traceroute(8) sends out either UDP or ICMP ECHO packets
with a TTL of one, and increments the TTL until the destination has been
reached. By printing the gateways that generate ICMP time exceeded messages
along the way, it is able to determine the path packets are taking to reach the
The problem is that with the widespread use of firewalls on the modern
Internet, many of the packets that traceroute(8) sends out end up being
filtered, making it impossible to completely trace the path to the destination.
However, in many cases, these firewalls will permit inbound TCP packets to
specific ports that hosts sitting behind the firewall are listening for
connections on. By sending out TCP SYN packets instead of UDP or ICMP ECHO
packets, tcptraceroute is able to bypass the most common firewall filters.
Generated by Doxygen 1.6.0 Back to index